問海頓 Piano Sonata in Eb major HOB XVI:49

Piano Sonata in Eb major HOB XVI:49 is one of the late compositions composed by Joseph Haydn.It is very difficult to describe Haydn's works one by one. However, the following information can help you to understand:
The development of sonata form into a subtle and flexible mode of musical expression – one that became the dominant force in Classical musical thought – owed most to Haydn and those who followed his ideas. His sense of formal inventiveness also led him to integrate the fugue into the classical style and to enrich the rondo form with more cohesive tonal logic (see sonata rondo form). Haydn was also the principal exponent of the double variation form – variations on two alternating themes, which are often major- and minor-mode versions of each other.

Haydn's work became central to what was later described as sonata form, and his work was central to taking the binary schematic of what was then called a "melodie". It was a form divided into sections, joined by important moments in the harmony which signalled the change. One of Haydn's important innovations (adopted by Mozart and Beethoven) was to make the moment of transition the focus of tremendous creativity. Instead of using stock devices to make the transition, Haydn would often find inventive ways to make the move between two expected keys.

Later musical theorists would codify the formal organization in the following way:


Introduction: If present in an extended form, a slower section in the tonic, often with material not directly related to the main themes, which would then rapidly transition to the
Exposition: Presentation of thematic material, including a progression of tonality away from the home key. Unlike Mozart and Beethoven, Haydn often wrote expositions where the music that establishes the new key is similar or identical to the opening theme: this is called monothematic sonata form.
Development: The thematic material is led through a rapidly shifting sequence of keys, transformed, fragmented, or combined with new material. If such a development is not present, the work is termed a "sonatina". Haydn's developments tend to be longer and more elaborate than those of Mozart, for example.
Recapitulation: Return to the home key, where the material of the exposition is re-presented. Haydn, unlike Mozart and Beethoven, often rearranges the order of themes compared to the exposition: he also frequently omits passages that appeared in the exposition (particularly in the monothematic case) and adds codas.
Coda: After the close of the recapitulation on the tonic, there may be an additional section which works through more of the possibilities of the thematic material.
During this period the written music was structured by tonality, and the sections of a work of the Classical era were marked by tonal cadences. The most important transitions between sections were from the exposition to the development and from the development to the recapitulation. Haydn focused on creating witty and often dramatic ways to effect these transitions, by delaying them, or by making them so subtle that it takes some time before it is established that the transition has occurred. Perhaps paradoxically, one of the ways in which Haydn achieved this was by reducing the range of devices used in harmonic transitions, so that he could explore and develop the possibilities of those he regarded as most interesting.

Perhaps this is why, more than any other composer's, Haydn's music is known for its humour. The most famous example is the sudden loud chord in the slow movement of his Surprise symphony, No. 94; Haydn's many other musical jokes include the false endings in the quartets Op. 33 No. 2 and Op. 50 No. 3, and the remarkable rhythmic illusion placed in the trio section of the third movement of Op. 50 No. 1.